In semiconductor device packaging, a metallic clip is often used to provide electrical connections between a semiconductor die and a lead frame to which the die is mounted. Most current clips are non-exposed clips. Some clips may be exposed for better heat dissipation, but have limitations. For example, U.S. Pat. No. 6,624,522 discloses a metal oxide semiconductor (MOS) gated device wafer having a source side covered with a passivation layer, preferably a photosensitive liquid epoxy, or a silicon nitride layer, or the like. The wafer is coated by a spinning, screening, or otherwise depositing the liquid epoxy onto the wafer surface. The material is then dried and the coated wafer is exposed using standard photolithographic techniques to image the wafer and openings are formed in the passivation layer to produce a plurality of spaced exposed surface areas of the underlying source metal and a similar opening to expose the underlying gate electrode of each die on the wafer. The passivation layer acts as a passivation layer and can further act as a plating resist (if required) and as a solder mask, designating and shaping the solder areas.
The wafer is then sawn or otherwise singulated into individual die. The individual die are then placed source-side down and a U-shaped or cup shaped, partially plated drain clip is connected to the solderable drain side of the die, using a conductive epoxy or solder, or the like to bond the drain clip to the bottom drain electrode of the die. The bottoms of the legs of the drain clip are coplanar with the source-side surface (that is the tops of the contact projections) of the die. The outer surface of the die is then over molded in a mold tray. After molding, the devices are tested, laser marked and sawn into individual devices. However, the devices are not compatible with standard lead frame pinouts.
U.S. Pat. No. 6,777,800 discloses semiconductor die package including a vertical power MOSFET having a gate region and a source region positioned at a bottom surface and a drain region positioned at a top surface. A gate lead electrically coupled to the gate region and a source lead electrically coupled to the source region. A drain clip is electrically coupled to the drain region. A non-conductive molding material encapsulates the semiconductor die, wherein a surface of the drain clip is exposed through the non-conductive molding material. However, this semiconductor die package requires flip-chip process.
US Patent Application Publication 20080087992 discloses a semiconductor package having a bridged plate interconnection. The package utilizes a bridged source plate interconnection having a bridge portion, valley portions disposed on either side of the bridge portion, plane portions disposed on either side of the valley portions and the bridge portion, and a connection portion depending from one of the plane portions. The bridge portion is disposed in a plane above the plane of the valley portions while the plane portions are disposed in a plane intermediate the plane of the bridge portion and the plane of the valley portions. During encapsulation, bonding material flows under the bridge portion and provides mechanical strength to the bridged source plate interconnection. The top of the bridge portion may be exposed through the molding compound, however the exposed area is small, which only allows a small heat dissipation path.
U.S. patent application Ser. No. 12/130,663 discloses a top exposed bridge clip including two or more separate electrically conductive fingers electrically connected to each other by one or more electrically conductive bridges. A first end of at least finger is adapted for electrical contact with a lead frame. A semiconductor device package may include the clip along with a semiconductor device and a lead frame. The semiconductor device may have a first and semiconductor regions on top and bottom surfaces respectively. The clip may be electrically connected to the top semiconductor region at the bridges and electrically connected to the lead frame at a first end of at least one of the fingers. However, this clip has small exposed area, which only allows a small heat dissipation path.
It would be desirable to develop a semiconductor device package that allows efficient heat dissipation, and has low resistance connections to the semiconductor device. It would be further desirable to develop a package that is compatible with standard semiconductor pinouts. It would be further desirable to make a semiconductor device package that has a rugged stress release structure, and has the flexibility to be used with differently sized semiconductor devices.
It is within this context that embodiments of the present invention arise.
In these drawings, common features shown in the figures are indicated by common reference numerals.